A cathode for use with a discharge plasma is a gas discharge device (e.g., a ring laser gyroscopes (RLG) cathode) has two wear-out mechanisms. The first is cathode sputter, and the second is cathode seal failure. Cathode sputter occurs when gas ions bombard the cathode during the running of the discharge in the ring laser gyroscope. The ion bombardment sputters metal from the cathode. At the same time, due to the biasing from the electrical source, the gas ions are temporarily held on the surface of the cathode. The metal sputtered from the cathode re-deposits on cooler areas of the cathode and on the block next to the cathode. When the metal sputtered from the cathode re-deposits on the cathode, it coats and traps the gas ions that are held on the surface of the cathode. This trapping of the gas ions decreases the life of the ring laser gyroscope by depleting the amount of gas available to maintain lasing and the discharge. A cathode sputter life for a currently available cathode is improved by increasing the inner diameter of the cathode.
The lifetime of the cathode seal is improved by increasing the annular width of the seal, which is often accomplished by decreasing the cathode inner diameter, increasing the cathode outer diameter, or both.
Prior art cathodes designed to address these wear-out mechanisms may be shorted by the plasma, which is shorted to the area that the cathode is intended to seal, and do not short to the larger inner diameter area as desired.